In the following example, Foo.pm lives in /tmp/foobar, Bar.pm and my_script.pl live in the current directory, and Bar inherits from Foo. Not that neither Foo.pm nor Bar.pm make reference to any directory.

# /tmp/foobar/Foo.pm
package Foo;

!! 'keep require happy';

sub baz {
  print 'Hello from ' . shift() . '::baz' . "\n";
}

__END__
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---

# ./Bar.pm
package Bar;
use base 'Foo';

!! 'keep require happy';

__END__
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---

# ./my_script.pl
use lib '/tmp/foobar';
use Bar;

Bar->baz();

__END__
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---

% perl my_script.pl
Hello from Bar::baz
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In fact, I can even omit the use lib line from my_script.pl, by invoking it with

% perl -I/tmp/foobar my_script.pl
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or

% perl -Mlib=/tmp/foobar my_script.pl
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